Plasticized copolymer compositions and process of producing same



Patented Sept. 5, 1950 PLASTICIZED'oOP LYMER COMPOSITIONS AND PROCESS OFPRODUCING SAME Albert M. 'Gessler, Qranford, N. 5., assignor to StandardOil Development manner Delaware i No Drawing.

This inyention relatcs to sy thetic rubber compositions and moreparticularly relates to plasticized diolefin-aromatic, olefin copolymercompo sitions and plasticized. diOlefin-olefin copolymer compositionsand methods of producing such plasticized compositions.

It isgenerally recognized that synthetic rubher-like copolyrners aremore 'difiicult to process than natural rubber because the syntheticcopolymers are extremely difficult to 'masticate'to a soft and plasticcondition which is necessaryffor proper compounding and processing intodesired articles. In order to Overcome this difliculty it has beennecessary to add'soiteners and plastif cizers to these syntheticrubber-like materials to improve their compounding and processingcharacteristics. It has generallybeen thought that softeners andplasticizers which are soluble or compatible with the syntheticrubber-likematerials must be used. Use of soluble plasticizers such asdibutyl phthalate and similar materials have not resulted in the desiredimproved processing characteristics.

According to this invention diolefin-aromatic olefin copolymers'anddiolefin-olefin cop-olymers are plasticized by using low molecularweight normally liquid butadiene-acrylonitrile copolymers (very viscousliquids, or semi-solids, not free flowing like water) which arepreferably made by an emulsion process. The low molecular weight oilydiolefin-acrylonitrile copolymer is'not mis- O cible with the rubberlike copolymer to beplasticized anddoes not have a solvating action ontherubber-like polymer but does havea plasticizing effect on the saidcopolymer.

-In .the prior art it is suggested that limited miscibility of. theplasticizer in-the rubber-like polymers is undesirable becauseit islsaidthat the plasticizer. Wouldj exude or sweat out from the polymers onstanding. This is true if the fluidity of the plasticizer is greatenough to allow for, its migration, by diffusion, through-the :molecularnetworkof the ,high polymer system. Byproper selection of the viscosityof the plastioizer, it has beenfound that such migration is reducedto'such prise diolefinaromatic olefin copolymers prea low magnitudethat, the plasticizing material p e y. n e ul on r qqe r om' maior pro:

Company, a corpo- Application December 10, 1947, Serial No. 790,935

13 oans. I (01. 26032.4)

portion of a conjugated diolefin, such as buta--' 'diene or i'soprene,or other diolefins having 4 to 6 carbon atoms per molecule and a minorproportion of styrene or substituted styrenes, such as alpha methylstyrene, para methyl styrene, 2,4- dichlorostyrene; and the like.

This invention is also applicable to rubbery polymers formed from C4 toC10 diolefins, such as butadiene-1,3, isoprene, piperylene, dimethylbutadiene, etc., and a C4-C1 olefin, such as isobutylene as set forth inThomas et al. Patent 2,356,128, issued August 22, 1944.

The emulsion process for preparing the butadiene-styrene type copolymersis well known and will only be briefly referred to. A latex is preparedby polymerizing a reactant mixture of a major proportion of a butadieneand a minor pro-' portion of a styrene in the ratio of about 3:1 inaqueous emulsion using 2:1 ratio of water to reactants with about 2 /2%by weight of a soap as an emulsifier, 0.25% by weight of a mixture ofC12 to C14 aliphatic mercaptans as polymerization modifiers and about0.2% of potassium persulfate as catalyst. The percentages given arebased on the water present in the emulsion. The proportions may beVaried and other emulsifiers, modifiers and catalysts may be used as iswell known in the art. The mixture is polymerized to about -80%conversion to polymer, the butadiene is then fiashed off and astabilizer, such as phenyl beta naphthylamine, is added. The latex isthen stripped of'monomeric' styrene. The temperature during the reactionis about 45 to 50 0., a1 though with: suitable activators lowertempera-' tures may be used. a r V The latex is coagulated byconcentrated sodium 'chloridesolutions or other brines, the polymerparticles filtered and dried at a temperature of about to C. and arethen ready for further processing in accordance with this invention. Thelow molecular weight normally liquid oily butadiene-acrylonitrilecopolymer which is used as the plasticizer is preferably made by anemulsion processas set forth in appending application filed June 11,1946, for Newberg et al. and bearingSerial Number 676,120. A majorproportion of C4-C6 conjugated diolefin, such as, butadiene, isoprene,piperylene, methyl pentadieneand di methyl butadiene, and a minorproportion of a nitrile of a low molecular weight unsaturated fattyacid, such as acrylonitrile or methacrylonitrile, are mixed in aqueousemulsion in the presence of 3 to 12% by weight on the monomers of analiphatic mercaptan of 6 to 16 carbon atoms. Tertiary mercaptans arepreferred to primary and secondary mercaptans but all three types may beused. For example, 3 to 8% by weight of tertiary mercaptans derived fromthe dimer of isobutylene may be used or about to 10% by weight of thetertiary mercaptan derived from the trime'r of isobutyl'ene or 7 to 12%by weight of tertiary mercaptan derived from the tetramer of isobutylenemay be used. Preferably, the tertiary mercaptans prepared fromdiisobutyle ne (dimer of isobutylene) are used. Other modifying agents,such as alkyl xanthogen po'lysulfides, may be used, but these are lessdesirable since they decrease the reaction rate very appreciably.Modifiers may be added all at once at the beginning of thepolymerization, continuously during the polymerization or only part maybe added at first and the rest added portion-wise or at a later timeduring the reaction.

It is also preferable but not essential to use highly unsaturated fattyacids, such as those obtained from linseed or soy bean oils, for thepreparation of soap emulsifiers. By using such soaps it is possible toreduce the amount of mercaptans or other modifiers used in the reaction.The amount of emulsifier is about 0.25 to 5% by weight and the amount ofpolymerization catalyst which may be potassium persulfate is about 0.1to 1% by weight based on the monomers. Other catalysts, such as hydrogenperoxide, al kali metal persulfates or perborates and ammoniumpersulfate or perb'orate may be used. The polymerization is carried outat about 30 to 35 C. buttemperatures as low as 10 C. may be used.

The dienes which are used in the preparation of the low molecular weightplasticizer comprise C4-C6 diolefins, such as butad-iene 1,3, isoprene,piperylene, methyl pentadiene, dimethyl butadiene, etc. The nitrile maybe acrylonitrile or methacrylonitrile or the like. d V

The copolymers prepared from mixtures containing 60 to 80% of thediolefin and from 40 to of the nitrile may be used in this invention.The copolymer containing to of acrylonitrile is the preferred one andmay be pre-- pared as follows:

' l l'parts by weight'of butadiene 26 parts by weight of acrylonit'rileI 4 parts by weight of sodium soapfo'f tauow acids fiparts by weight ofoctyl zrfercaptan 0:3 part by weight of potassium persulfate 200 partsby weight of water The above mixture is heated at about '30 "C. for 17hours in a pressure bottlewh'ile shaking to form a latex. The latex isstabilized by the addition of 0.5% by weight based on the polymer of2,6-di-tertiary butyl para cresol. The latex is coagul'ated with 200parts by weight "of sodium chloride brine, washed withisoprop'yl'alcohol and water and then dried at about 125 C. A nor mallyliquid viscous oil is obtained in "a yield equivalent 'to about 79% ofthe monomers of the feed'. The product which is liquid at harm-a1temperatures contained about 28% often-b1 d acrylonitrile and had anintrinsic viscosity or about"0.l8. These viscous oily coiziolym'ersuseful in this invention are oily liquids even when the "reaction iscarried to 80 'to 90% monomer conversion and have intrinsic viscositiesbetween about 0.15 'a-nd 0.60.

(1) The intrinsic viscosity is determined as follows:

where [Nl-intrinsic viscosity lnnatural logarithm Nrrelative viscosityand is the ratio of (2) The molecular weight is calculated from theintrinsic viscosity as follows:

[N] ="4.9 m wwhere M equals molecular weight.

The M so calculated is approximately the true number average molecularweight and is roughly ten times the Staudinger numbers frequently quotedas molecular weights.

(3) Using the equation given under (2), an intrinsic viscosity range of0.15-0.6 would correspond to a molecular weight range of about 7,400-69,000.

The kinematic viscosity of the viscous oil used in the examples belowwas 6,700 centistokesat 212 F. and its intrinsic viscosity was 0.18. Thekinematic viscosity may vary from 5000 to 20,000 ce'ntistokes at 212 F.The oily viscous copolymer having kinematic viscosities between 5000 to10,000 centistokes at 212 F. are preferred in this invention.

The oily low molecular weight diene-nitrile.

plasticizing material above described may be incorporated in therubbery. copolymer on an ordinary open mill, on a calender, inanextruder, in a Banbury mixer or the like. Instead of adding theplasticizer to the dried rubber-y material, the oily low molecularweight plasticizer is made in emulsion form and may be added in theemulsion form to the butadiene-styrene copolymer also in emulsion formor in latex form so that upon coagulation of the mixture with sodiumchloride brine or the like the plasticizer is distributed in the rubberycopolymer and there is obtained a very uniform mixture of plasticizer inthe, diolefin-styrene copolymer.

In working up butadie'ne-styrene copolymers with formerly usedplasticizers it has been ordinarily necessary to first subject thecopolymer to mastication. in a, Banbury mixer for several minutes tobreak down the copolymer. and to cause it to band readily on a mill.After this preliminary mastication, a small portion of the softener orplasticizer was added and the mill or, mixer was again operated for afewminutes. The addition of 'the plasticizer caused lacing and breakingapart of the copolymer on the mill. Additional amounts of plasticizercould only be added after other compounding ingredients and furthermixing and working was e'fiec'ted. Specifically this applies to theaddition ofdibutyl phthalate to the 'b'utadie'ne-styren'e copolymer andthe time of adding the dibutyl 'phthalate increases almost linearly withthe amount added or concentrated in the copolymer.

The following data compare the 'plastioi'zin'g or processing effect ofdibu-tyl phthalate in which on s lbutadiene styrene copolymer) solubleand 'oilyviscous 'butadiene' acrylonitrile'; copolymer' which isinsoluble or immiscible-with GR -S copolymen The oily viscousbutadiene-acrylo'- nitrile polymer used in this workwas made by theemulsion process as set forth -aboveand contained about 72% butadieneand 28% acrylonitrile and had an intrinsic viscosity of about 0.18 and akinematic viscosity of about 6700 centistokes at 212 F.

The GRr-S copolymer was made by'an emulsion process and containedapproximately' 75% butadiene, 25% styrene, and had a Mooney viscosity of50 as determined at 100 C. a

The oily low molecular weight butadieneacrylonitrile copolymer will bereferred toin the following data as Oily Polymer. The amounts ofplasticizer and'GR-S'are parts by weight.

These mixtures were prepared on a 6'' 1; 12"

laboratory mill operating at a 1:1;4 speed ratio.

other premast'ication treatments." The plasticizer used in thisinvention is a very viscous liquid or semi-solid at an ordinarytemperature and may be added rapidly to the rubbery polymer on the mill.This oily plasticizing polymer used in the above cited examples is avery viscous liquid with the consistency of heavy honey or molasses.Dibutyl phthalate, on the other hand, is a low viscosity liquid not muchmore viscous than water, the viscosity of dibutyl phthalate being 2.3centistokes at 212 F.

'As has just been pointed out, the rapid addition of a plasticizer to arubber on a mill is a function: of the viscosity of the plasticizer anddoes not depend to agreat extent on solubility therein. The smoothnessof the band on the mill and the activity of the bankj-on theother hand,depend completely on solubility characteristics. The GR-Si:(butadiene-styrene rubbery copolymer) oily polymer blends werecharacterized by good A-1780-1 A-l782-1 A-1782-2 A-1782-3 'A71782-4Amer-5 oR-s 100.0 100.0 100.0 1100.0 100.0 100.0 DibutylPhthalate--- 05.0 10 0 15.0 20.0 25.

. i-ioso-i A-1950-2' A-1950-3 A-1950-47A-l950-5 ore-s 100.0 100.0 100.000.0 'io o' Oily Polymer 5.0 10.0 15.0 20.0 J- t 25. Q

There was no evidence in all of the A-l950blendsmill behavior. The. bankwas in all cases'active that a condition of incompatibility existed. androlling; a sheet cut from the mill was very The mixtures of the polymersystems just given 1 smooth and showed relatively no elastic shrinkwereprepared as stated above and the time to age. The elastic-plasticcharacteristics of the complete the mix is indicated in minutes below:polymersystems; will now be described.

' Total After the various polymer-plasticizer systems 1 7 Time ormixtures which have been shown. above had ij z gj gggggggfi: en made andthe time data had been collected, A-l782-3 Polymer banded in 4' gofieneraggegingif im not; 40 each-stock was milled again for varying periodsfijggfi g ggggg g gg toobtam for all a constant period of abo t 15A-1950-1 Oily polymer addedin 1% minutesiof mechanical treatment. 950-'2g g g fg gg s i f f Z 10 1%; relative iomhstic properties of the4-1950-3 out pievious form} ho n g6 systems already prepared W111 now bediscussed. A -1950-4 mm ofban X P Y I v The'plastmity of the polymercomposition has an 1 :19 m V ----d 1 2 important bearing upon the rateat which it can .In order to get rid or all holes in the 100% be md l elength of product extruded GR-S polymer band, the polymer had to bemilled mm P l and the enslonalstability of 8 minutes. The milling m theabove data started th ud product. h dlmensional bi ity at 95-100" F.Cooling water was kept on through- 13 a property of great importancesince it is Obviout the milling. The final temperature was about 3desirable and n c y h he compound to F. The 0 polymer was be readilyfabricated dimensionally within the milled for 15 minutes like the othersystems for limits of the Specifications. e question of purposes ofcomparison as will be hereinafter shape and final dimension of theextruded prodpomted 7 n I ucts is dependent wholly on theelastic-plastic Addition of dibutyl phthalate to GR-S (butaproperties ofthe p lym r sys m b n handled. diene-styrene copolymer) on an open millwas The distortion of an extruded item as it difficult. The matrixpolymer had to be handed issues from the die of. the extruder isdethorou ghly first, since even small portions of the to pendent on itstendency to recover from the softener or plasticizer when added causedthe deformation induced, i. e., on the developpolymer to break apart andlace. The time to ment of the reversible, high elastic component adddibutyl phthalate increased almost linearly 'of its deformation. Thiscomponent attains full with its concentration. The GR-S(butadienedevelopment slowly, particularly if the stock is styrenerubbery copolymer) on the. mill banded allowed to cool. In manyinstances where the momentarily, then after a half minute or solacedextruded item is passed directly into a cold water due'to heat buildup.After 4 minutes, the band quench trough, the development of the highelaswas again formed with only small holes in it. tic component isarrested'sharply'and'the rub- The oily polymer used as the plasticizerwas added ber retains its shape until it is again heated durdirectly tothe matrix polymer, the addition-hav- '7 ing the early stages ofvulcanization and the reing been started before the lacing began A greatadvantage in saving time is obtained when'a plasticizer can be addeddirectly to an unbandedor untreated rubbery polymer on a mill. It allowsfor the-elimination of breakdown and covery can'continue to completion.In'order to allow for the full development of thishigh-elastic-component of deformation, i. e., for complete lateral swelland longitudinal shrinkage; all the tubes' formed' the experimentsdescribed-be low were given a minute heat treatment immediatelyfollowing their extrusion.

The extrusion experiments described below were carried out with the useof a'# Boyle extruder. The machine was set in such a way that the wormturned 80 revolutions per minute and steam was supplied to the head andbarrel so that both were maintained at 220 F. A threaded die with aninside forming diameter of 0.4 inch was fastened to the head of theextruder over a core bridge fixed with a core whose outside formingdiameter was 0.3 inch. The extruded article, therefore, was a tubehaving a theoretical outside diameter of 0.4 inch and a theoretical wallthickness of 0.05 inch.

For the test work, stock sheeted from a mill and cut in thin strips wasfed into the extruder. The initially formed tube collected at the headof the machine was fed back to the worm for a second pass to insureequilibrium thermal conditions throughout. On the third pass through thetuber, duplicate sections of the tube were taken every 30 seconds untiltwo nearly perfect checks were obtained. From the extruder, the two tubesections were taken directly to an air oven maintained at about 220 F.and allowed to rest for ten minutes on a liberally talced base. Afterthe heat period, the tubes were cooled for five minutes at roomtemperature and their weight and length measured. From the specificgravity of the stock, and the measurements of weight and length taken,the volume in cubic centimeters per inch of the tube was calculated. Amaterial, if it were completely plastic, would extrude exactly to diedimensions and would have a volume per inch of 0.9 cc. This value,therefore, would be the ideal value representing the case of purelyplastic behavior; elastictendencies of the polymer systems would resultin tube volumes which would be larger than this ideal value, the elastictendency being proportional to the volume increase. This expression ofvolume shows in precise, quantitative terms the swell of the variouspolymer-plasticizer systems tested.

The results of the above tests are given in Table 1, wherein the postextrusion swell of the tube is expressed (as the volume per inch ofextruded material) as a function of the plasticizer concentration. TheGR-S polymer is 100 parts by weight in each case and the plasticizersare in parts by weight.

GR-S

Taking first the blends containing the solvent the mixtures during. theextrusion operation. With the immiscible plasticizer, the lowmolecularweight oily polymer (butadiene-acrylonitrile), the elasticityof the resulting systems has decreased rapidly with increasingconcentrations of the plasticizeix, The excellent processing propertieswhich naturally originate from this decreased elasticity would show upas well in all fabrication operations. Calendered sheets, for example,have been found to be smooth and to show a minimum of post calendershrinkage tendencies.

Furthermore, the extruded tubes from the mixtures containing dibutylphthalate were of irregular outer contour, the tube wall was thick andthe central hole'was small and irregularly shaped (pentagonal from thespider), whereas the extruded tubes from the mixtures containing theoily low molecular weight polymer plasticizer had a much smoother outercontourlespecially those using 10 or more parts of plasticizer), a thintube wall with a circular central opening.

To further develop these extrusion results and to show that they are notjust functions of the rate of flow of material through the extruder thefollowing data are given:

For a given polymer or polymer system, the swell,. as a result ofelastic behavior, of the formed tube would increase as the rate ofextrusion increased. In this case all systems were tubed using aconstant speed of R. P. M. on the extruder worm screw. From these facts,then, it is even more striking that the GR-S polymer-low molecularweight oily polymer systems show such a drastic reduction in elasticquality when at the same time the rate of passage through the extruderincreases so sharply.

As previously stated, the plasticizers of this invention are also usefulin plasticizing polydiene-olefin rubbery copolymers such as theisob'utylene-diolefln copolymers. Such a copolymer was prepared asfollows: 97 parts of isobutylene and 3 parts of isoprene were dissolvedin 150 parts of methyl chloride and cooled to a temperature of 100 C. byexternal cooling with ethylene. Catalyst consistingof a 0.5% solution ofaluminum chloride in methyl chloride was added with good agitation untila conversion of approximately 70% of theory was obtained. The reactionmixture was quenched by pouring into boiling water, and the rubberyparticles slurried with approximately 2% of zinc stearate and 0.25% of"phenyl beta naphthylamine. The polymer crumbs were filtered and dried.The raw polymer had a Mooney viscosity of about 45 at 100 C.

The diolefin-isoolefin rubbery copolymer prepared as above, was mixedwith plasticizers on a 6" x 12" laboratory mill operated at a 1:1.4speed ratio and at substantially the same temperatures as abovedescribed in connection with the butadiene-s-tyrene copolymer. Thefollowing mixtures were prepared with the different amounts ofplasticizers set forth below, the GR-I being theisobutylene-isoprenerubbery copolymer and the oily polymer being thesame as above described in connection with the butadiene-styrenecopolymer. V J

The hydrocarbon oil-Zerice 42-is a solvent .for the GRJ rubber and hasthe following properties: A. .P. I. gravity of 24.3", flash point of 355F., Saybolt Universal viscosity of 158.7 at 100." F. and 41.7 at 210 F.,and an anilinepoint of 173 F. The oily polymer is a low molecular weightbutadiene-acrylonitrile copolymer which hasan intrinsic viscosity ofabout. 0.18 and is immiscible with GR-I rubber. Butyl requires nopremastication treatment; 100% butyl milled for same timeas othersystems.

Addition of the hydrocarbon solvent to the matrix polymer on the millwas difiicult. As is usual in the case of low viscosity esterplasticizers, the material :had to be added very slowly to prevent thestock'from breaking apart or lacing. The total time to complete theincorporation of the hydrocarbon solvent was proportional to itsconcentration. The oily polymer could be added very rapidly to theisobutyleneisoprene copolymer (GR-I) rubber on the mill. No lacingtendencies were encountered. The time to make the addition remainedconstant for all practical purposes, over the range of concentrationsshown.

After the plasticizers had been incorporated with the polymer, millingwas continued in each case for varying intervals so that each system wasgiven the same overall mechanical treatment. It was desired to show therelative elasticity of the two types of systems shown above. For

.this purpose, the extrusion plasticity test described above inconnection with the butadienestyrene copolymer was used. In this test,the rubbery polymers were extruded under very carefully controlledconditions-to form a tube.

The results of these tests are given in Table2 wherein the postextrusion swell of the tube ex- -pressed as the volume per inch iscompared with the plasticizer concentration and type.

Table 2 Volume in cc. per inch of extruded material Hydrocar- Oily Poly:bon solvent,

Polymer, 100 parts by wt.

parts by Wt.

OOHOHDOJrhGOMW Taking first the blends containing the hydrocarbonsolvent plasticizer, itcan be seen that :the distortion of the formedtube has become somewhat greater as the concentration .of-theplasticizer was" increased. What this means, of

course, is that the raw polymer, already highly elastic, has become moreelastic with-the addition of the solvent plasticizer. In the case oftheimmiscible dipolymer systems prepared with GR-I and the low molecularweight oilypolymer plasticizer, the post swell or elasticity of theextruded tube has fallen 01f rapidly as the concentration of oilyplasticizer was increased. It has approached very soon the range ofexcellent extrusion performance, which performance can be obtained onlywith systems characterized by high plasticity and low elasticity.

In addition, the tubes formed from the mixture containing the lowmolecular weight oily copolymer had truer dimensions, that is, the tubewall was thinner, the outer contour was smoother and rounder, and thecentral hole was circular.

For a given polymer or polymer system, the swell of the formed tube willbe increased as the rate of extrusion is increased. This is just anotherway of saying that the elastic-plastic tendencies of polymer systems, asthey are measured by deformation studies, are dependent on the rate ofstress application. From this, it might be expected that for theGR-I-low molecular weight oily copolymer system shown above, slowerrates of extrusion would be obtained than were obtained for the GR-Ihydrocarbon holv'ent system. That this was not the case is shown in thefollowing table: (number designation of mixtures refers to mixturescited above).

Rate of Rate of Extru- Extru- Mixture sion Mixture sion (Inches/(Inches/ Min.) Min.)

As can be seen, the rate of extrusion-has remained substantiallyconstant over the whole range of the hydrocarbon solvent concentrationsgiven above. With low molecular weight oily polymer, however, the rateof extrusion increased sharply as the concentration of the oily polymerwas increased.

The amount of oily viscous low molecular bu- -tadiene-acrylonitrilecopolymer plasticizer which may be used varies between about 5 parts byweight to 50 parts by weight per 100 partsby weight of thepolydiene-styrene copolymer or polydiene-olefin copolymer. If thepolydieneolefin copolymer is not highly unsaturated, having an iodinevalue below about 50, some difiiculty may arise in the curing orvulcanizing'of the polydiene-olefin copolymer if too much ofthebutadiene-acrylonitrile plasticizer is used 'and therefore for bestresults the amount of the oily copolymer is maintained between about 5and 10 parts by'weight per 100 parts by weight of the polydiene-olefincopolymen However,

' where the product is used in instances where the curing is not afactor or where more unsaturated diene-olefin polymers are employed,amounts up to about 30 parts by weight of the oily. copolymer per partsby weight of the polydiene-olefin copolymer'may be used. The intrinsicviscosity of the oily viscous butadieneacrylonitrile copolymer which isuseful as a plasticizer or softener in this invention may vary betweenabout 0.15 to 0.6 andits kinematic vis- 'cosity is between about 5000and 20;,000- centistokes at 212 F.

of about 250- centistokes at 212 F., it isunsuited .for this processbecause it exudes or bleeds from the GR-I or GR-S polymer. If highmolecular weight butadiene-acrylonitrile polymer suchas standardPerbunan-Zfi is used as a- 'plasticizer, noprocessing improvements areobtained with either GR-I or GR-S, the extrusion rate being low and theelastic swellbeing high. From this it will be seen that the intrinsic;viscosity range of. the oily polymer plasticizer is important forobtaining the improved results flowing from the use of the process ofthe present invention.

The extruded or milled material containing: the plasticizer of thisinvention and the polydienearomatic olefin may be cured or vulcanizedtoproduce rubbery products where the plasticizer is used in the rangeabove given.

The addition of fillers, such as carbon blacks and clays, and of zincoxide, etc; is made much easier with previous addition ofoily polymerplasticizer. Thetendency for the stock to lace during these additionsdisappears; Because of the active, rolling bank and the even, smoothband,. better dispersion of such materials is obtainedand lesstime isrequired to complete the mix.

The oily butadiene-acrylonitrile polymer plasticizer may also be usedfor plasticizing polydienes, such as polybutadiene, polyisoprene,natural rubber, and the like.

While low temperatures are preferred during milling, improved resultsare obtained with the plasticizers of the present invention at thetemperatures used in the milling of the particular material.

range of 95 F. to 150 F; being preferred. While there are given severalembodiments of this invention, it is to be understood that variousmodifications and changes may bemade without departing from the spiritof the invention.

It is claimed:

1. A composition of matter comprising 100 parts by weight of a rubberyhydrocarbon poly:- mer of an unsaturated aliphatic hydrocarbon materialcontaining at least one'do'uble bond and about 5' to 50 parts by weightof a plasticizing or softening agent which does not have a solvatingcous copolymer of 60 to 80% of butadiene with 40 to 20% of acrylonitrilehaving an intrinsic viscosity in the range between .l5 and" 0.6.

3. A composition of matter comprising a rubbery hydrocarbon polymer of aconjugated diolefin and a plasticizing agent in an amount in the rangebetween and 50 parts by weight per 100 parts by weight of said polymer,said plasticizing agent comprising a normally liquidbutadieneacrylonitrile copolymer having an intrinsic viscosity between0.15 and 0.6.

The temperature during milling may range between about 95 F; and 400 F.,with the ,4. A. composition according to claim 3: wherein the rubberypolymer comprises isobutylene copolymerized with a 04-010 conjugateddiolefin and the plasticizing agent is used in an amount in the rangebetween 5 and parts by: weight per 100 parts b weight of said polymer.

5. A composition: of matter comprising 100 parts by weight of asynthetic rubbery copolymer of a major proportion of a conjugateddiolefin of from 4 t0 6 carbon atoms per molecule and a minor proportionof styrene and about 5 to 30 parts by weight of a pl-asticizing agentcomprising a viscous normally oily copolymer of 60 to 80% of butadieneand to 20% of acrylonitrile having amolecular weight in the range of anintrinsic viscosity of 0.15 to 0.6.

' 6. A composition of matter comprising a, synthetic rubbery copolymerof a major proportion of isobutyl'ene and a minor proportion of isopreneand 5 to 10 parts of a plasticizer comprising a normally oily viscousbutadiene-acrylonitrile copolymer having an intrinsic viscosity in therange between about 0.15 and'0.6.

'7". A composition of matter comprising 100 parts by weight of asynthetic rubber-like c0- polymer of an olefin and a diolefin and 5 to30 parts by weight of a plasticizer comprising a low molecular weightnormally liquid viscous copolymer of a conjugated C4-C6 diolefin and anitrile selected from the group consisting of acrylonitrile andmethacrylonitrile having an intrinsic viscosity not less than about0.15.

v 8'. A process for improving the workability of a synthetic rubberyhydrocarbon polymer of olefinic material containing'a-t least one doublebond which comprises masticating the polymer at a temperature betweenabout 95 F. and 400 F., together with a plasticizing agent comprising'anormally liquid viscous butadiene-acrylonitrile copolymer having anintrinsic viscosity in the range between 0.15 and 0.6 to produce a homogeneous mixture.

9. A process for improving the workability of a synthetic rubberyhydrocarbon copolymer of a conjugated diolefin and an olefinic materialcopolymerizable therewith which comprises adding to said copolymer 5 to30 parts by weight per I00 parts by weight of said copolymer of 3,normally liquid viscous copolymer of a major proportion of butadiene anda minor proportion of acrylonitrile having an intrinsic viscosity in therange between 0.15 and 0.6 and milling the resulting mixture at atemperature between 95 F. and 400 F. to produce a homogeneous mixture.

10. A process for improving the mill behavior of synthetic rubber-likecopolymers of a, major proportion of a C4 to C6. conjugated diolefin anda minor proportion of a styrene which comprises adding from 5 to byweight of an oily viscous butadiene-acrylonitrile copolymer having anintrinsic viscosity in the range between 0.15 and 0.6 and subjecting theresulting mixture to a mastication treatment at a temperature between 95and 400 F. to produce a homogeneous mixture.

11. A process for improving the workability of a synthetic rubberycopolymer of a major proportion of butadiene and a minor proportion ofstyrene which comprises adding to 100 parts by weight of said copolymer5 to 30 parts by weight of a normally liquid viscous emulsion copolymerof to of butadiene and 40 to 20% of acrylonitrile having an intrinsicviscosity in the range between 0.15 and 0.6 and subjecting the resultingmixture to a kneading and milling of isoprene which comprises adding tosaid Number Name Date polymer a plasticizing amount of a viscous bu a-2,217,631 Wolfe Oct. 8, 1940 diene-acrylonitrile copolymer having anintrinsic m 1 viscosity in the range between about 0.15 and 0.6 OREIGNPATENTS and subjecting the resulting mixture to a masti- 10 NumberCountry Date cation treatment at a temperature in the range 705,104Germany Apr. 17, 1941 13 14 action at a temperature between 95 and 150F; to REFERENCES CITED produce homogeneous mlxture' The followingreferences are of record in the 12. A process for improving theworkability of a synthetic rubbery hydrocarbon polymer of a file of thlspatent major portion of isobutylene and a minor portion UNITED STATESPATENTS between about 95 F. and 400 F. to produce a homogeneous mixture.

13. A process according to claim 12 wherein the temperature duringmastication is within the 15 range between 95 F. and 150 F.

ALBERT M. GESSLER.

1. A COMPOSITION OF MATTER COMPRISING 100 PARTS BY WEIGHT OF A RUBBERYHYDROCARBON POLYMER OF AN UNSATURATED ALIPHATIC HYDROCARBON MATERIALCONTAINING AT LEAST ONE DOUBLE BOND AND ABOUT 5 TO 50 PARTS BY WEIGHT OFA PLASTICIZING OR SOFTENING AGENT WHICH DOES NOT HAVE A SOLVATING EFFECTON SAID POLYMER AND WHICH COMPRISES A VISCOUS NORMALLY LIQUID COPOLYMEROF A CONJUGATED C4-C6 DIOLEFIN AND A NITRILE SELECTED FROM THE GROUPCONSISTING OF ACRYIONITRILE AND METHACRYLONITRILE HAVING A MOLECULARWEIGHT IN THE RANGE OF AN INTRINSIC VISOSITY BETWEEN 0.15 AND 0.6.